Genetics The Language of Life Image from: http://commons.wikimedia.org/wiki/File:Hazel_eye.jpg
Genetics, The Unit How these genes are passed from generation to generation. (inherited) How genes affect the way we look and Function. What’s the probability of a gene being inherited? How we can manipulate genes to get desired outcomes
Genetics, Clarified How we get the Genes we get (Genes?) Gene: A section of DNA that encodes for a trait. (Trait?) Trait: Information communicated by the DNA. Sometimes obvious (eye color), sometimes hidden (enzymes). The gene is a sequence of the DNA, the trait is what the DNA encodes for, or “makes”.
For example: Eye color Alleles: The different “forms” a gene may have Important point: a gene actually encodes for a protein. “One gene: one protein”
http://commons.wikimedia.org/wiki/File:Chromosomes.JPG http://upload.wikimedia.org/wikipedia/commons/9/91/Chromosome.gif Organization in the Nucleus • Long strands of chromatincondense into chromosomes. • The sister chromatids are the result of replication. • Each chromatid has the same base sequence • Histone proteins act as spools
Chromosomes Chromosomes are generally represented as being shaped like an “X”. They are actually 2 chromatids joined together like conjoined twins. The result of replication of one chromatid Chromatid The shorter part of the “X” is the “p” arm The spot where the 2 chromatids join is called the centromere The longer part of the “X” is the “q” arm
How many? Most of the cells in our body have 46 (23 pair) chromosomes. Exception: Our Gametes (egg and sperm) have 23 single chromosomes
How many? Gametes (haploid) Diploid Zygote (fertilized egg)
Some Vocabulary • Gene • Allele • Zygote • Gamete Section of DNA that codes for a trait (actually, they code for protein strands but more on that later) Different “forms” of a gene (brown eyes vs. blue eyes) fertilized egg (alleles in pairs) sex cells i.e. sperm and eggs (single alleles)
http://www.nlm.nih.gov/visibleproofs/media/detailed/vi_a_201.jpghttp://www.nlm.nih.gov/visibleproofs/media/detailed/vi_a_201.jpg http://upload.wikimedia.org/wikipedia/commons/b/b7/Snow_Pea_on_Plant.JPG MendelA monk and his peas • Mid 19th century Austrian • Developed a basic understanding of inheritance of traits. • Followed traits in generations of pea plants
http://commons.wikimedia.org/wiki/File:Mendel_seven_characters.svghttp://commons.wikimedia.org/wiki/File:Mendel_seven_characters.svg Following the Traits
Mendel’s “Laws” • Genes for traits comein pairs(one from each parent). • Law of dominance – one gene (allele) can prevent the appearance of another gene (allele). • Law of segregation – when gametes form, pairs of genes separate so each gamete gets one of each gene pair. • Law of independent assortment – During gamete formation, genes for different traits separate independently of one another.
More Vocabulary Having different alleles in an allelic pair (Bb) AKA hybrid Both alleles in the pair are the same (BB, bb) AKA pure The allele that is expressed (shown) in a heterozygous pair of alleles The allele that is NOT expressed in the heterozygous pair of alleles • Heterozygous • Homozygous • Dominant • Recessive
Even More Vocabulary The physical traits that are expressed in an individual e.g. brown eyes The alleles present in an individual e.g. BB or Bb • Phenotype • Genotype *Phenotype does not always show genotype Brown eyes = BB or Bb So how do we figure out our genotype? More on that…next class
For instance: What’s the genotype? RR The phenotype? Homozygous red Red Rr What’s the genotype? Heterozygous red The phenotype? Red What’s the genotype? rr The phenotype? White Homozygous white